The invention relates to a band saw blade tensioning machine with a measuring station for measuring the tension in the band saw blade, comprising a flat support for the blade, and a tensioning station for rolling tension into the band saw blade.
Band saw blade straightening machines such as those disclosed, for example, in U.S. Pat. No. 4,852,430 yield very good results with considerably reduced handling. Apart from the need that they be as free from unevenness as possible, the second prerequisite for band saw blades is that they have a defined tension contained in the band saw blade. This tension substantially consists in the circumferential length of the band saw blade being largest in the median range between back and teeth and in decreasing outwards in both directions. This tension is needed to ensure that the band saw blade lies optimally on the curved circumferential surfaces of the blade drive wheels.
Another important prerequisite is the straightness of the back and of the front of the teeth. Both the tension and the straightness can be rolled by means of suitable rolling processes along circumferential lines in the band saw blade.
In WO-A-92/19407 a tensioning or truing machine for band saw blades is disclosed. This machine has a tension measuring device which detects the tension in the blades and a processing unit which contains a pair of tensioning rollers moveable across the blade to effect the necessary rolling along the circumferential lines of the blades. The applied pressure of the tensioning rollers is controlled in dependency of the detected tension. The measuring device is positioned at a location, where the saw blade is curved and where, thus, the longitudinal tension results in a curvature across the blade. This curvature is concave at the lower surface of the blade where the measurement is effected. This has certain disadvantages because the measurements has to be made from underneath.
It is therefore an object of the invention to provide a band saw tensioning machine able to roll tension in an automated working sequence into the band saw blade, which avoids the disadvantages of the previously known systems.